1. Field of the Invention
The present invention relates to operational amplifier, in particular to an operational amplifier that is a compensated dynamically.
2. Description of Related Art
Operational amplifier (opamp in short) is an important circuit building block for numerous applications. Depending on its target application, an opamp usually needs to satisfy a list of requirements, for example: DC gain, unit-gain bandwidth, phase margin, slew-rate, and so on. Opamp is usually used in a closed-loop circuit configuration, where the overall circuit accuracy and linearity is determined by its DC gain, and the overall circuit speed is determined by unit-gain bandwidth (for small signal input) or slew-rate (for large signal input), while the stability of the circuit is determined by the phase margin. It is very difficult to design a high DC gain amplifier with a high unit-gain bandwidth and/or a high slew-rate while at the same time having a comfortable stability margin. To ensure good stability, compensation technique is usually employed in an opamp design. Compensation, however, reduces the unit-gain bandwidth and/or the slew rate.
What is needed is a dynamic compensation technique for opamp where the compensation is performed depending on the state of the signal processing.